Take-off mechanisms are utilized to remove a sheet of stock from a press bed of a silk screen printing press or the like after each press cycle. These take-off mechanisms generally include grippers mounted on a reciprocating carriage which serve to remove printed stock by gripping the stock as the carriage moves adjacent the printing press and thereafter releasing the stock onto a drying bed or rack as the carriage travels a desired distance away from the printing press. Typically, the grippers are fixed in position on a traverse shaft or similar support member of the carriage and are actuated by engaging a ramp, dog or other similar structure on the take-off frame. To expose a leading edge of the stock to facilitate removal, the take-off mechanisms may operate in communication with drop edge mechanisms and lift members on the press which are mechanically linked to the take-off frame or in cooperation with cutouts on the press bed.
An example of one such assembly is illustrated in U.S. Pat. No. 4,512,563which discloses a take-off apparatus having a carriage with a plurality of grippers mounted on a common transverse shaft where the gripper jaws of the grippers are opened in unison by rotation of the transverse shaft. The shaft rotates by engaging a ramp mounted to the take-off frame. To assist in the pick-up and removal of a printed sheet of stock from the printing press, a leading edge of the printed sheet is raised by a plurality of pins driven upward by a pin drive mechanism. The pin drive mechanism is mechanically linked to the take-off and is actuated by the approaching carriage.
Such an assembly, however, does not permit adjusting the position of each of the gripper bars either laterally or longitudinally to provide for ready removal of irregularly shaped sheets. Further, the assembly does not provide for selectively controlling the take-off carriage and the pin drive mechanism independently one from the other.
It therefore would be desirable to provide adjustable gripper bars on the carriage where each may be independently repositioned laterally or longitudinally to readily accommodate variations in the shape, position, and size of the stock. It also would be desirable to provide grippers with adjustably spaced jaws for removing stock with varying thicknesses. To provide for manual stock removal and selective operation of the take-off, it would further be desirable to control the operation of the take-off carriage and grippers independently of the printing press and lift pins. In addition, it would be desirable for the carriage to be moved at a high speed after the gripper jaws have gripped the forward edge of the printed stock to the position for release of the printed stock and to move slowly toward the lifted forward edge of the printed stock for gripping the lifted edge.